| Objective:In the present study, we investigated the prevalence of HBoV and the genome HBoV load in the respiratory tract aspirates obtained from hospitalized children with wheezing and other lower respiratory tract infection and tried to find out whether HBoV is a"passenger"or real pathogen in children with lower respiratory tract infections, particularly in childhood wheezing diseases.Methods:1. From April 2006 to January 2010, 136 children with wheezing were enrolled in this study. Meanwhile, 50 hospitalized children with other respiratory diseases without wheezing were selected as control. The lower respiratory tract aspirates were collected by flexible bronchoscopy.2. Direct immunofluorescence assay (DFA) was used for diagnosis of adenovirus.respiratory syncytial virus ,influenza A and B,parainfluenza 1,2,3 infection.3. DNA virus detection: DNA was extracted from 200μl aliquot of each sample by using QIAamp ? DNA Mini Kit (QIAGEN Inc, USA) and detected by PCR.4. RNA virus detection: RNA was extracted from 200μl supernatant of each sample by using QIAamp ? RNA Mini Kit (QIAGEN Inc, USA) and detected by PT-PCR.5. Real-Time PCR for HBoV: A TaqMan real-time PCR experiment targeting the NP-1 region of HBoV was conducted to quantify viral load in HBoV positive respiratory aspirates.6. Statistical analysis:Data on the descriptive characteristics of the children were analyzed byχ2.Data on the quantitative data of the children were analyzed by Mann-Whitney U-test , two-sample t-test. For all outcomes and relations between variables, differences between groups were considered statistically significant at P <0.05. SPSS (version 17.0) was used for all analysis.Results:1. General information:Totally 186 lower respiratory tract aspirates were collected through April 2006 to January 2010. 136 children with wheezing were enrolled as W group. The 136 children were prospectively studied, aged from1 month to 141months, with a median age of 10 months, 68 of whom were male. 50 children were enrolled as control group(C group). 28 were boys in this group. Those children were between 3 months and 169 months, with a median age of 16 months.2. Virus detected in lower respiratory tract aspirates:Out of 186 lower respiratory tract aspirates, 61were negative for both direct fluorescence assay and PCR. All the samples were negative for PIV-2 detection.The PIV-3,RSV,HBoV,RV were top four virus detected, no matter with co-infection or not.HBoV was detected positive in 31 samples. Sole detection of HBoV was positive in 14 patients. The frequency of codetection among HBoV-positive samples with other viral pathogens was 55% (17/31). The most common viruses coinfected with HBoV were RSV, RV, PIV-3 and ADV.HBoV predominantly circulated during the winter season. HBoV was detected in every month except September through the year, and peaked in the month of December. Most children infected with HBoV are in the age group from 6 to 24 months. The children infected with HBoV aged from 4 months to 169 months, with an average age of 16.41±5.61 months.3. HBoV viral load:HBoV genome copies of the 31 HBoV-PCR positive samples ranged from 5.02^102 to5.26^109 copies/ml lower respiratory tract aspirate by realtime-PCR.The percentage of cases with a high HBoV load was 32%(10/31).The percentage of cases with a low HBoV load was 68%(21/31).The average of HBoV load of HBoV positive samples from C-group and W-group were 4.35^103±1.72^103,2.58^107±1.89^107 copies/ml lower respiratory tract aspirate. The median of them were 2290.47,13342.83 copies/ml lower respiratory tract aspirate.HBoV load of samples collected from W-group was significantly higher than those from C-group (P=0.01).4. Clinical characteristics of HBoV infection in children with wheezing:All the samples with a high HBoV load were named as"high viral load-group". Analogically, all the samples with a low HBoV load were named as"low viral load-group".The average duration of hospitalization of children from the"high load-group"were significant longer than that of children from the"low viral load-group"(P<0.05).The clinical score of respiratory system of those two groups were also compared, no significant difference were found (P>0.05).Children with a high HBoV load have more cases wheezed longer than 4 weeks than those with a low HBoV load (P<0.05).Conclusion:1. The percentage of HBoV infection in children with lower respirtory infection in Chongqing area was 17%. The frequency of codetection among HBoV-positive samples with other viral pathogens was 55%. The most common virus coinfected with HBoV was RSV, RV, PIV-3 and ADV.2. Circulation of HBoV predominantly during the winter season. Most children infected with HBoV were in the age group from 6 to 24 months.3. HBoV load of samples collected from W-group was significantly higher than those from C-group (P=0.01).High load of HBoV in respiratory aspirates correspond with the duration of hospitalization in children with wheezing. Children with a high HBoV load have more cases wheezed longer than 4 weeks than those with a low HBoV load (P=0.01). These facts showed that wheezing is a important clinical manifestation of HBoV infection. When the genome HBoV load in the respiratory tract aspirates is high,HBoV probably play the role of pathogen in lower respiratory infection in children. |
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